Whoever controls the flow of information controls the deal. That's why tough deal-makers are notoriously tight-lipped. But if you must give up a secret, consider a confidentiality (nondisclosure) agreement. It'll specify what is secret and who does and doesn't get to know.

What is confidential? If you're the one with the secrets, the broader the definition, the better. If you're on the other side, however, that all-encompassing definition can hurt you. It's generally unfair to ask someone to keep confidential information that becomes publicly available, information they already have, information they got from someone else who has nothing to do with the deal, information they developed on their own or information they may be required by law to disclose.

Who must keep the secret? Obviously, the greater the number of people who know, the greater the possibility of a leak. It's appropriate to limit disclosures to those who need to help make the deal and will respect confidence.

For how long is it secret? That depends. Some secrets, such as financial information, go stale. Other information, particularly trade secrets, like the formula for Coca-Cola, does not. Flexibility is key. As the recipient, the longer you have to keep a secret, the greater the chance you'll slip up.

A speaker and attorney in Los Angeles, Marc Diener is author of Deal Power.